package cn.texous.util.commons.util;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Md5 util
 */
public class Md5Util {

    //MD5的字符串常量
    private static String[] hexDigits = {
            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
            "a", "b", "c", "d", "e", "f"};

    /***/
    public static String md5Hex(String plainText) {
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            String result = byteArrayToHexString(messageDigest.digest(plainText.getBytes()));
            return result;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return null;
    }

    /***/
    private static String byteArrayToHexString(byte[] b) {
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++) {
            resultSb.append(byteToHexString(b[i]));
        }
        return resultSb.toString();
    }

    /**
     * 将一个字节转化成十六进制形式的字符串
     */
    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0)
            n = 256 + n;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    /***/
    public static byte[] getKeyedDigest(byte[] buffer, byte[] key) {
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            md5.update(buffer);
            return md5.digest(key);
        } catch (NoSuchAlgorithmException expected) {
        }
        return null;
    }

    /***/
    public static String getKeyedDigest(String strSrc, String key) {
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            md5.update(strSrc.getBytes("UTF8"));
            String result = "";
            byte[] temp;

            temp = md5.digest(key.getBytes("UTF8"));
            for (int i = 0; i < temp.length; i++) {
                result += Integer.toHexString((0x000000ff & temp[i]) | 0xffffff00).substring(6);
            }
            return result;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /***/
    public static String md5(String strSrc) {
        return getKeyedDigest(strSrc, "");
    }

}
